There is a terribly clumsy approach that might do this, but nobody has thought it necessary enough to make a product to do just what you want.

Xantech has a device that will receive a Xantech IR code, then spit out an RS232 code. And another one that will receive an RS232 code and spit out a learned IR code. The glitch here is (I think) that you have to start out with Xantech codes, so this might not work. And the hardware could run hundreds of dollars.

www.xantech.com